Hydrolyzed divinylbenzene/maleic anhydride polymeric sorbents for carbon dioxide

ABSTRACT

Methods of sorbing carbon dioxide on porous, hydrolyzed divinylbenzene/maleic anhydride polymeric sorbents are provided. Additionally, compositions resulting from sorbing carbon dioxide on porous, hydrolyzed divinylbenzene/maleic anhydride polymeric sorbents are provided. The porous polymeric sorbents typically have micropores, mesopores, or a combination thereof and can selectively remove carbon dioxide from other gases such as methane or hydrogen.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing under 35 U.S.C. 371 ofPCT/US2016/036869, filed Jun. 10, 2016, which claims the benefit of U.S.Provisional Application No. 62/182,067, filed Jun. 19, 2015, thedisclosure of which is incorporated by reference in its/their entiretyherein.

TECHNICAL FIELD

Methods of sorbing carbon dioxide and compositions resulting fromsorbing carbon dioxide on porous, hydrolyzed divinylbenzene/maleicanhydride polymeric sorbents are provided.

BACKGROUND

The production of energy from coal and natural gas requires technologiesto remove carbon dioxide (CO₂), which is a gaseous impurity in bothprocesses. The low cost and global abundance of both coal and naturalgas all but ensures the continued use of these two natural resources forenergy generation for many years to come. Efforts to developtechnologies to improve the removal of unwanted CO₂ through thedevelopment of selective, high capacity sorbents for CO₂ are needed.

To generate energy from coal, integrated gasification combined cycle(IGCC) power plants make use of the water-gas shift reaction. Coal isburned and the carbon monoxide produced is then reacted with water in areactor containing a catalyst to perform the water-gas shift reaction.This reaction converts water and carbon monoxide to carbon dioxide andhydrogen. The CO₂/H₂ gas stream produced (called synthetic gas orsyngas) typically contains about 35-40 mole percent CO₂. An importantstep in electricity generation at IGCC power plants is the removal ofthe carbon dioxide generated by the water-gas shift reaction to producefuel grade or even higher purity hydrogen. The hydrogen is subsequentlyused to power a combined cycle turbine that produces electricity.

The most widely used method to remove the CO₂ from H₂ is a pressureswing adsorption cycle with the sorbent being a physical solvent. In apressure swing adsorption cycle, a CO₂/H₂ gas stream at high pressure(e.g., 20-45 bar) is passed through the physical solvent resulting in apurified H₂ stream exiting the sorbent vessel. The adsorption portion ofthe cycle is stopped prior to breakthrough of a targeted level of CO₂. Adesorption step is then performed to regenerate the physical solvent.

Physical solvents separate CO₂ from other gases based on a difference insolubility. Because there are only weak interactions between the CO₂ andthe physical solvent, the CO₂ can be easily removed from the physicalsolvent by reducing the pressure. While there are several differentphysical solvents in use today, polyethylene glycol dimethyl ether(available under the trade designation SELEXOL) is the most commonlyused. While the adsorption selectivity for CO₂ is high, the solubilityof CO₂ in SELEXOL at 20 bar and 25° C. is only about 9.6 weight percent.Although the solubility amount can vary depending on the temperature andpressure used in the process, the ability to capture a higher percentageof CO₂ per mass of sorbent while maintaining selectivity over othergases such as hydrogen would be highly advantageous.

Natural gas production requires an extensive set of processes to purifythe natural gas to a useable fuel. Typical impurities include acid gases(such as hydrogen sulfide and sulfur dioxide), water, and carbondioxide. Carbon dioxide is typically present in natural gas at a levelclose to 5 volume percent. While the most common method to remove CO₂from methane is a pressure swing adsorption cycle, the low partialpressure of the CO₂ in the mixture makes the removal of CO₂ withphysical solvents impractical. A stronger interaction between the CO₂and solvent is required. As such, chemical solvents are typically used.The most widely used chemical solvent is an aqueous solution of ethanolamine. In a single pressure swing adsorption cycle, ethanol amine canseparate/capture about 5 percent of its mass in CO₂. While the stronginteraction of the CO₂ with the chemical solvent allows for theefficient removal of the CO₂ from the gas stream, regeneration of thechemical solvent requires heating. This heating step tends to render theoverall process energetically expensive.

Polymeric materials prepared from divinylbenzene and maleic anhydridehave been known for many years. Many of these polymeric materials areprepared by a process called macroreticulation, which refers to aprocess of making polymeric beads using suspension polymerization. Theseprocesses involve forming droplets of an organic phase suspended in anaqueous phase. The suspended organic phase includes the monomers and anoptional porogen. The maleic anhydride content in the final copolymerhas been low, however, because this monomer tends to undergo hydrolysisand leave the organic phase. Attempts to reduce the hydrolysis reactionhave included replacing the aqueous phase with glycerol or other polarsolvents. Macroporous copolymers have been prepared.

SUMMARY

Methods of sorbing carbon dioxide on porous, hydrolyzeddivinylbenzene/maleic anhydride polymeric sorbents are provided.Additionally, compositions resulting from sorbing carbon dioxide onporous, hydrolyzed divinylbenzene/maleic anhydride polymeric sorbentsare provided. The porous polymeric sorbents typically have micropores,mesopores, or a combination thereof and can selectively remove carbondioxide from other gases such as methane or hydrogen.

In a first aspect, a method of sorbing carbon dioxide on a porouspolymeric sorbent is provided. The method includes providing a polymericsorbent having a BET specific surface area equal to at least 250m²/gram. The porous polymeric sorbent contains (a) 8 to 40 weightpercent of a first monomeric unit of Formula (I),

(b) 48 to 75 weight percent of a second monomeric unit of Formula (II),

(c) 0 to 20 weight percent of a third monomeric unit of Formula (III)wherein R¹ is hydrogen or alkyl,

and (d) 0 to 8 weight percent of a fourth monomeric unit of Formula(IV).

Each weight percent value is based on a total weight of the porouspolymeric sorbent. Each asterisk (*) denotes the location of attachmentof the monomeric unit to another monomeric unit or to a terminal group.The method further includes exposing the porous polymeric sorbent to agas mixture containing carbon dioxide and sorbing carbon dioxide on theporous polymeric sorbent.

In a second aspect, a composition is provided that includes (a) a porouspolymeric sorbent having a BET specific surface area equal to at least250 m²/gram and (b) carbon dioxide sorbed on the porous polymericsorbent. The porous polymeric sorbent contains (a) 8 to 40 weightpercent of a first monomeric unit of Formula (I),

(b) 48 to 75 weight percent of a second monomeric unit of Formula (II),

(c) 0 to 20 weight percent of a third monomeric unit of Formula (III)wherein R¹ is hydrogen or alkyl,

and (d) 0 to 8 weight percent of a fourth monomeric unit of Formula(IV).

Each weight percent value is based on a total weight of the porouspolymeric sorbent. Each asterisk (*) denotes the location of attachmentof the monomeric unit to another monomeric unit or to a terminal group.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot of the adsorption and desorption isotherms at 25° C.and at pressures up to about 20 bar for both carbon dioxide and methaneon an exemplary porous polymeric sorbent.

FIG. 2 is the argon adsorption isotherm at 77° K and at relativepressures up to 0.98±0.01 for an exemplary porous polymeric sorbent.

DETAILED DESCRIPTION

Methods of sorbing carbon dioxide on porous, hydrolyzeddivinylbenzene/maleic anhydride polymeric sorbents are provided.Additionally, compositions resulting from sorbing carbon dioxide onporous, hydrolyzed divinylbenzene/maleic anhydride polymeric sorbentsare provided. The porous polymeric sorbents typically have micropores,mesopores, or a combination thereof and can selectively remove carbondioxide from other gases such as methane or hydrogen.

The terms “a”, “an”, and “the” are used interchangeably with “at leastone” to mean one or more of the elements being described.

The term “and/or” means either or both. For example “A and/or B” meansonly A, only B, or both A and B.

The terms “polymer” and “polymeric material” are used interchangeablyand refer to materials formed by reacting one or more monomers. Theterms include homopolymers, copolymers, terpolymers, or the like.Likewise, the terms “polymerize” and “polymerizing” refer to the processof making a polymeric material that can be a homopolymer, copolymer,terpolymer, or the like.

The terms “polymeric sorbent” and “porous polymeric sorbent” are usedinterchangeably to refer to a polymeric material that is porous and thatcan sorb gaseous substances such as, for example, carbon dioxide. Porousmaterials such as the polymeric sorbents can be characterized based onthe size of their pores. The term “micropores” refers to pores having adiameter less than 2 nanometers. The term “mesopores” refers to poreshaving a diameter in a range of 2 to 50 nanometers. The term“macropores” refers to pores having a diameter greater than 50nanometers. The porosity of a polymeric sorbent can be characterizedfrom an adsorption isotherm of an inert gas such as nitrogen or argon bythe porous material under cryogenic conditions (i.e., liquid nitrogen at77° K). The adsorption isotherm is typically obtained by measuringadsorption of the inert gas such as argon by the porous polymericsorbent at multiple relative pressures in a range of about 10⁻⁶ to about0.98±0.01. The isotherms are then analyzed using various methods such asBET (Brunauer-Emmett-Teller method) to calculate specific surface areasand such as density functional theory (DFT) to characterize the porosityand the pore size distribution. The term “sorbing” and similar wordssuch as “sorbs” and “sorbed” refer to the addition of a first substance(e.g., a gas such as carbon dioxide, hydrogen, or methane) to a secondsubstance (e.g., a polymeric material such as the porous polymericsorbent) by adsorbing, absorbing, or both. Likewise, the term “sorbent”refers to a second substance that sorbs a first substance by adsorbing,absorbing, or both.

The term “surface area” refers to the total area of a surface of amaterial including the internal surfaces of accessible pores. Thesurface area is typically calculated from adsorption isotherms obtainedby measuring the amount of an inert gas such as nitrogen or argon thatadsorbs on the surface of a material under cryogenic conditions (i.e.,liquid nitrogen 77° K) over a range of relative pressures. The term “BETspecific surface area” is the surface area per gram of a material thatis typically calculated from adsorption isotherm data of the inert gasover a relative pressure range of 0.05 to 0.30 using the BET method.

The term “monomer mixture” refers to that portion of a polymerizablecomposition that includes the monomers. More specifically, the monomermixture includes at least divinylbenzene and maleic anhydride. The term“polymerizable composition” includes all materials included in thereaction mixture used to form the polymeric material. The polymerizablecomposition includes, for example, the monomer mixture, the organicsolvent, the initiator, and other optional components. Some of thecomponents in the polymerizable composition such as the organic solventmay not undergo a chemical reaction but can influence the chemicalreaction and the resulting polymeric material.

The term “divinylbenzene/maleic anhydride polymeric material” refers toa polymeric material prepared from divinylbenzene, maleic anhydride, andoptionally a styrene-type monomer. Styrene-type monomers are oftenpresent as impurities in divinylbenzene.

The term “styrene-type monomer” refers to styrene, an alkyl substitutedstyrene (e.g., ethyl styrene), or mixtures thereof. These monomers areoften present in divinylbenzene as impurities.

The term “room temperature” refers to a temperature in a range of 20° C.to 30° C., in a range of 20° C. to 25° C., in a range close to 25° C.,or 25° C.

A method of sorbing carbon dioxide is provided. The carbon dioxide issorbed on a porous polymeric sorbent that includes (a) 8 to 40 weightpercent of a first monomeric unit of Formula (I),

(b) 48 to 75 weight percent of a second monomeric unit of Formula (II),

(c) 0 to 20 weight percent of a third monomeric unit of Formula (III)wherein R¹ is hydrogen or alkyl,

and (d) 0 to 8 weight percent of a fourth monomeric unit of Formula(IV).

Each weight percent value is based on a total weight of the porouspolymeric sorbent. Each asterisk (*) denotes the location of attachmentof the monomeric unit to another monomeric unit or to a terminal group.The carbon dioxide can be sorbed at room temperature or at any desiredtemperature such as in a range of −30° C. to 150° C. or in a range of−20° C. to 50° C.

The porous polymeric sorbent is a hydrolyzed polymeric material formedfrom a non-hydrolyzed precursor polymer prepared from divinylbenzene,maleic anhydride, and an optional styrene-type monomer. Thenon-hydrolyzed precursor polymeric material, which can be referred to asa divinylbenzene/maleic anhydride polymeric material or as a precursorpolymeric material, is treated with a hydrolyzing agent to prepare thehydrolyzed polymeric material. The conditions used to synthesize theprecursor polymeric material are specifically selected to produce ahydrolyzed polymeric sorbent that has high BET specific surface area(e.g., equal to at least 250 m²/gram).

The non-hydrolyzed precursor polymeric material (i.e., thedivinylbenzene/maleic anhydride polymeric material) is synthesized froma monomer mixture of maleic anhydride, divinylbenzene, and an optionalstyrene-type monomer. More specifically, the non-hydrolyzed polymericmaterial is formed from a monomer mixture containing 1) 8 to 40 weightpercent maleic anhydride, 2) 48 to 75 weight percent divinylbenzene, and3) 0 to 20 weight percent or a styrene-type monomer, wherein thestyrene-type monomer is styrene, an alkyl substituted styrene, or acombination thereof. The amounts are based on the total weight ofmonomers in the monomer mixture.

The maleic anhydride that is included in the monomer mixture used toform the non-hydrolyzed precursor polymeric material results in theformation of maleic anhydride monomeric units of Formula (IV).

These maleic anhydride monomeric units of Formula (IV) are hydrolyzed toform the monomeric units of Formula (I)

in the polymeric sorbent. Some of the maleic anhydride monomeric unit ofFormula (IV) may remain in the polymeric sorbent if the hydrolysisreaction is not 100 percent complete. The divinylbenzene that isincluded in the monomer mixture used to form the non-hydrolyzedprecursor polymeric material is the source of the monomeric units ofFormula (II) in the polymeric sorbent. Any optional styrene-typemonomers that are included in the monomer mixture used to form thenon-hydrolyzed precursor polymeric material are the source of themonomeric units of Formula (III) in the polymeric sorbent.

The amount of maleic anhydride used in the monomer mixture to preparethe precursor polymeric material determines the number of carboxylicacid functional groups in the hydrolyzed polymeric material, which isthe porous polymeric sorbent. Each maleic anhydride monomeric unit ofFormula (IV) included in the non-hydrolyzed precursor polymeric materialcan result in the formation of a monomeric unit of Formula (I) havingtwo carboxylic acid groups (—COOH groups) in the polymeric sorbent. Themonomer units of Formula (I) may enhance the solubility of carbondioxide in the polymeric sorbent and may influence the total amount ofcarbon dioxide that is sorbed. If the amount of monomeric units ofFormula (I) is less than 8 weight percent based on a total weight of thepolymeric sorbent, the solubility of carbon dioxide in the polymericsorbent may be unacceptably low. On the other hand, if the amount ofmonomeric units of Formula (I) is greater than 40 weight percent basedon the total weight of the polymeric sorbent, the BET specific surfacearea may be too low. If the BET specific surface area is too low, theamount of carbon dioxide sorbed on the polymeric sorbent may beunacceptably low.

In some embodiments, the amount of the monomeric units of Formula (I) isat least 8 weight percent, at least 10 weight percent, at least 12weight percent, at least 15 weight percent, or at least 20 weightpercent. The amount of the monomeric units of Formula (I) can be up to40 weight percent, up to 38 weight percent, up to 35 weight percent, upto 30 weight percent, or up to 25 weight percent. For example, themonomeric units of Formula (I) may be present in a range of 8 to 40weight percent, 8 to 38 weight percent, 10 to 40 weight percent, 10 to35 weight percent, 10 to 30 weight percent, 10 to 25 weight percent, 15to 40 weight percent, 15 to 35 weight percent, 15 to 30 weight percent,15 to 25 weight percent, 20 to 40 weight percent, 20 to 35 weightpercent, or 20 to 30 weight percent. The amounts are based on the totalweight of the polymeric sorbent.

In some embodiments, all (i.e., 100 weight percent) of the maleicanhydride monomeric units of Formula (IV) in the non-hydrolyzedprecursor polymeric material are converted to first monomeric units ofFormula (I) in the porous polymeric sorbent. In other embodiments, atleast 80 weight percent of the maleic anhydride units in the precursorpolymeric material are converted to first monomeric units of Formula(I). For example, the percent conversion to first monomeric units ofFormula (I) can be at least 85 weight percent, at least 90 weightpercent, at least 95 weight percent, at least 97 weight percent, atleast 98 weight percent, or at least 99 weight percent based on thetotal weight of maleic anhydride units of Formula (IV) in the precursorpolymeric material. Thus, in some embodiments, the polymeric sorbent cancontain up to 8 weight percent monomeric units of Formula (IV) based ona total weight of the polymeric sorbent. For example, the polymericsorbent can contain 0 to 8 weight percent, 0.1 to 8 weight percent, 0.5to 8 weight percent, 1 to 8 weight percent, 1.5 to 8 weight percent, 0to 7 weight percent, 0.1 to 7 weight percent, 1 to 7 weight percent, 1.5to 7 weight percent, 0 to 6 weight percent, 0.1 to 6 weight percent, 1to 6 weight percent, 1.5 to 6 weight percent, 0 to 4 weight percent, 0.1to 4 weight percent, 1 to 4 weight percent, 1.5 to 4 weight percent, 0to 2 weight percent, or 0.1 to 2 weight percent maleic anhydridemonomeric units of Formula (IV).

The amount of the monomeric units of Formula (II), which are from thedivinylbenzene included in the monomer mixture used to form theprecursor polymeric material, can have a strong influence on the BETspecific surface area of both the precursor polymeric material and thepolymeric sorbent. The monomeric units of Formula (II) contribute to thehigh crosslink density and to the formation of a rigid polymericmaterial having micropores and/or mesopores. The BET specific surfacearea tends to increase with an increase in the amount of divinylbenzenein the monomer mixture used to form the precursor polymeric material andwith the resulting amount of monomeric units of Formula (II) in thepolymeric sorbent. If the amount of monomeric units of Formula (II) isless than 48 weight percent, the polymeric sorbent may not have asufficiently high BET specific surface area. On the other hand, if theamount of monomeric units of Formula (II) is greater than 75 weightpercent, the solubility of the carbon dioxide in the polymeric sorbentmay be compromised due to the decreased amount of monomeric units ofFormula (I).

In some embodiments, the amount of monomeric units of Formula (II) is atleast 48 weight percent, at least 50 weight percent, at least 55 weightpercent, or at least 60 weight percent. The amount of monomeric units ofFormula (II) can be up to 75 weight percent, up to 70 weight percent, orup to 65 weight percent. For example, the monomeric units of Formula(II) can be in a range of 48 to 75 weight percent, 50 to 75 weightpercent, 50 to 70 weight percent, 50 to 65 weight percent, 55 to 75weight percent, 55 to 70 weight percent, 55 to 65 weight percent, 60 to75 weight percent, or 60 to 70 weight percent. The amounts are based onthe total weight of the polymeric sorbent. In some specific embodiments,the amount of monomeric units of Formula (II) is in a range of 50 to 65weight percent based on the total weight of the polymeric sorbent.

Divinylbenzene, which is the source of the monomeric units of Formula(II), can be difficult to obtain in a pure form. For example,divinylbenzene is often commercially available with purity as low as 55weight percent. Obtaining divinylbenzene with purity greater than about80 weight percent can be difficult and/or expensive. The impuritiesaccompanying divinylbenzene are typically styrene-type monomers such asstyrene, alkyl substituted styrene (e.g., ethyl styrene), or mixturesthereof. Thus, styrene-type monomers are often present along withdivinylbenzene and maleic anhydride in the monomer mixture used to formthe precursor polymeric material. The monomer mixture typically contains0 to 20 weight percent styrene-type monomers based on a total weight ofmonomers in the monomer mixture. If the content of the styrene-typemonomer is greater than 20 weight percent, the crosslink density may betoo low and/or the distance between crosslinks may be too large toprovide a polymeric sorbent with the desired high BET specific surfacearea (e.g., at least 250 m²/grams). As the crosslink density decreases,the polymeric sorbent tends to be less rigid and less porous.

Typically, divinylbenzene having a purity of 55 weight percent is notsuitable for use in the monomer mixtures used to form the precursorpolymeric material because the content of styrene-type monomerimpurities is too high. That is, to provide a monomer mixture having aminimum amount of 48 weight percent divinylbenzene, the divinylbenzeneoften is at least about 80 weight percent pure. Using divinylbenzenehaving a lower purity than about 80 weight percent can result in theformation of a precursor polymeric material and/or a hydrolyzedpolymeric material with an undesirably low BET specific surface area.

In some embodiments, the amount of monomeric units of Formula (III),which result from styrene-type monomers used to form the precursorpolymeric material, is at least 1 weight percent, at least 2 weightpercent, or at least 5 weight percent. The amount of monomeric units ofFormula (III) can be up to 20 weight percent, up to 15 weight percent,up to 12 weight percent, or up to 10 weight percent. For example, theamount of monomeric units of Formula (III) can be in a range of 0 to 20weight percent, 1 to 20 weight percent, 2 to 20 weight percent, 5 to 20weight percent, 5 to 15 weight percent, or 10 to 15 weight percent. Theamounts are based on the total weight of the polymeric sorbent.

Overall, the polymeric sorbent includes 8 to 40 weight percent monomericunits of Formula (I), 48 to 75 weight percent monomeric units of Formula(II), 0 to 20 weight percent monomeric units of Formula (III), and 0 to8 weight percent monomeric units of Formula (IV). In other embodiments,the polymeric sorbent contains 10 to 40 weight percent monomeric unitsof Formula (I), 50 to 75 weight percent monomeric units of Formula (II),1 to 20 weight percent monomeric units of Formula (III), and 0 to 8weight percent monomeric units of Formula (IV). In other embodiments,the polymeric sorbent contains 15 to 35 weight percent monomeric unitsof Formula (I), 55 to 75 weight percent monomeric units of Formula (II),1 to 20 weight percent monomeric units of Formula (III), and 0 to 7weight percent monomeric units of Formula (IV). In still otherembodiments, the polymeric sorbent contains 20 to 30 weight percentmonomeric units of Formula (I), 55 to 75 weight percent monomeric unitsof Formula (II), 1 to 20 weight percent monomeric units of Formula(III), and 0 to 6 weight percent monomeric units of Formula (IV). Infurther embodiments, the polymeric sorbent contains 20 to 35 weightpercent monomeric units of Formula (I), 55 to 70 weight percentmonomeric units of Formula (II), 1 to 20 weight percent monomeric unitsof Formula (III), and 0 to 7 weight percent monomeric units of Formula(IV). In still further embodiments, the polymeric sorbent contains 20 to40 weight percent monomeric units of Formula (I), 50 to 70 weightpercent monomeric units of Formula (II), 5 to 20 weight percentmonomeric units of Formula (III), and 0 to 8 weight percent monomericunits of Formula (IV). The weight percent values are based on the totalweight of the polymeric sorbent.

Stated differently, the polymeric sorbent is formed by hydrolysis of theprecursor polymeric material. The precursor polymeric material is formedfrom a monomer mixture that includes 8 to 40 weight percent maleicanhydride, 48 to 75 weight percent divinylbenzene, and 0 to 20 weightpercent styrene-type monomer. In other embodiments, the monomer mixturecontains 10 to 40 weight percent maleic anhydride, 50 to 75 weightpercent divinylbenzene, and 1 to 20 weight percent styrene-type monomer.In other embodiments, the monomer mixture contains 15 to 35 weightpercent maleic anhydride, 55 to 75 weight percent divinylbenzene, and 1to 20 weight percent styrene-type monomer. In still other embodiments,the monomer mixture contains 20 to 30 weight percent maleic anhydride,55 to 75 weight percent divinylbenzene, and 1 to 20 weight percentstyrene-type monomer. In further embodiments, the monomer mixturecontains 20 to 35 weight percent maleic anhydride, 55 to 70 weightpercent divinylbenzene, and 1 to 20 weight percent styrene-typemonomers. In still further embodiments, the monomer mixture contains 20to 40 weight percent maleic anhydride, 50 to 70 weight percentdivinylbenzene, and 5 to 20 weight percent styrene-type monomer. Theweight percent values are based on a total weight of monomers in themonomer composition. At least 80 weight percent (e.g., at least 85weight percent, at least 90 weight percent, at least 95 weight percent,at least 97 weight percent, at least 98 weight percent, or at least 99weight percent) of the maleic anhydride monomeric units of Formula (IV)in the precursor polymeric material are hydrolyzed to the monomericunits of Formula (I) during the formation of the porous polymericsorbent.

Typically, at least 95 weight percent of the monomeric units included inthe polymeric sorbent are selected from Formula (I), Formula (II),Formula (III), and Formula (IV). For example, at least 97 weightpercent, at least 98 weight percent, at least 99 weight percent, atleast 99.5 weight percent, at least 99.9 weight percent, or 100 weightpercent of the monomeric units included in the polymeric sorbent areselected from Formula (I), Formula (II), Formula (III), or Formula (IV).In many embodiments, the only monomeric units purposefully included inthe polymeric sorbent are of Formula (I) or Formula (II) with any othermonomeric units being present because of impurities in the monomers usedto form the precursor polymeric material (including monomeric units ofFormula (III)) or because of incomplete conversion of the monomericunits of Formula (IV) to those of Formula (I). In some embodiments,where high purity divinylbenzene is used, the monomer mixture containsonly divinylbenzene and maleic anhydride. That is, the sum of themonomeric units in the polymeric sorbent are only of Formula (I),Formula (II), and Formula (IV).

Stated differently, the monomer mixture used to form the precursorpolymeric material typically contains at least 95 weight percentmonomers selected from maleic anhydride, divinylbenzene, andstyrene-type monomer. For example, at least 97 weight percent, at least98 weight percent, at least 99 weight percent, at least 99.5 weightpercent, at least 99.9 weight percent, or 100 weight percent of themonomers in the monomer mixture are selected from maleic anhydride,divinylbenzene, and styrene-type monomer. In some embodiments, wherehigh purity divinylbenzene is used, the monomer mixture contains onlydivinylbenzene and maleic anhydride. That is, the sum of the amount ofdivinylbenzene and maleic anhydride is 100 weight percent.

In addition to the monomer mixture, the polymerizable composition usedto form the non-hydrolyzed precursor polymeric material includes anorganic solvent. The polymerizable composition is a single phase priorto polymerization. Stated differently, prior to polymerization, thepolymerizable composition is not a suspension. The organic solvent isselected to dissolve the monomers included in the monomer mixture and tosolubilize the precursor polymeric material as it begins to form. Theorganic solvent includes a ketone, ester, acetonitrile, or mixturethereof. The organic solvent can function as a porogen during theformation of the precursor polymeric material. The organic solventchoice can strongly influence the BET specific surface area and the sizeof the pores formed in the non-hydrolyzed precursor polymeric material.Using organic solvents that are miscible with both the monomers and theforming polymer tend to result in the formation of polymeric materialhaving micropores and mesopores. Good solvents for the monomers and theforming polymer tend to result in a larger fraction of the porosity ofthe final polymeric sorbent being in the form of micropores andmesopores.

Organic solvents that are particularly suitable include ketones, esters,acetonitrile, and mixtures thereof. Provided that the resultingprecursor polymeric material has a BET specific surface area equal to atleast 350 m²/gram or even equal to at least 400 m²/gram, other organicsolvents can be added along with one or more of these organic solvents.Examples of suitable ketones include, but are not limited to, alkylketones such as methyl ethyl ketone and methyl isobutyl ketone. Examplesof suitable esters include, but are not limited to, acetate esters suchas ethyl acetate, propyl acetate, butyl acetate, amyl acetate, andtert-butyl acetate.

The organic solvent can be used in any desired amount. The polymerizablecompositions often have percent solids in a range of 1 to 75 weightpercent (i.e., the polymerizable composition contains 25 to 99 weightpercent organic solvent). If the percent solids are too low, thepolymerization time may become undesirably long. The percent solids areoften at least 1 weight percent, at least 2 weight percent, at least 5weight percent, at least 10 weight percent, or at least 15 weightpercent. If the weight percent solids is too great, however, theviscosity may be too high for effective mixing. Further, increasing thepercent solids tends to result in the formation of polymeric materialwith a lower BET specific surface area. The percent solids can be up to75 weight percent, up to 70 weight percent, up to 60 weight percent, upto 50 weight percent, up to 40 weight percent, up to 30 weight percent,or up to 25 weight percent. For example, the percent solids can be in arange of 5 to 75 weight percent, 5 to 50 weight percent, 5 to 40 weightpercent, 5 to 30 weight percent, or 5 to 25 weight percent.

In addition to the monomer mixture and organic solvent, thepolymerizable compositions typically include an initiator for freeradical polymerization reactions. Any suitable free radical initiatorcan be used. Suitable free radical initiators are typically selected tobe miscible with the monomers included in the polymerizable composition.In some embodiments, the free radical initiator is a thermal initiatorthat can be activated at a temperature above room temperature. In otherembodiments, the free radical initiator is a redox initiator. Becausethe polymerization reaction is a free radical reaction, it is desirableto minimize the amount of oxygen in the polymerizable composition.

Both the type and amount of initiator can affect the polymerizationrate. In general, increasing the amount of the initiator tends to lowerthe BET specific surface area; however, if the amount of initiator istoo low, it may be difficult to obtain high conversions of the monomersto polymeric material. The free radical initiator is typically presentin an amount in a range of 0.05 to 10 weight percent, 0.05 to 8 weightpercent, 0.05 to 5 weight percent, 0.1 to 10 weight percent, 0.1 to 8weight percent, 0.1 to 5 weight percent, 0.5 to 10 weight percent, 0.5to 8 weight percent, 0.5 to 5 weight percent, 1 to 10 weight percent, 1to 8 weight percent, or 1 to 5 weight percent. The weight percent isbased on a total weight of monomers in the polymerizable composition.

Suitable thermal initiators include organic peroxides and azo compounds.Example azo compounds include, but are not limited to, thosecommercially available under the trade designation VAZO from E.I. duPont de Nemours & Co. (Wilmington, Del.) such as VAZO 64(2,2′-azobis(isobutyronitrile)), which is often referred to as AIBN, andVAZO 52 (2,2′-azobis(2,4-dimethylpentanenitrile)). Other azo compoundsare commercially available from Wako Chemicals USA, Inc. (Richmond, Va.)such as V-601 (dimethyl 2,2′-azobis(2-methylproprionate)), V-65(2,2′-azobis(2,4-dimethyl valeronitrile)), and V-59(2,2′-azobis(2-methylbutyronitrile)). Organic peroxides include, but arenot limited to, bis(1-oxoaryl)peroxides such as benzoyl peroxide (BPO),bis(1-oxoalkyl)peroxides such as lauroyl peroxide, and dialkyl peroxidessuch as dicumyl peroxide or di-tert-butyl peroxide and mixtures thereof.The temperature needed to activate the thermal initiator is often in arange of 25° C. to 160° C., in a range of 30° C. to 150° C., in a rangeof 40° C. to 150° C., in a range of 50° C. to 150° C., in a range of 50°C. to 120° C., or in a range of 50° C. to 110° C.

Suitable redox initiators include arylsulfinate salts, triarylsulfoniumsalts, or N,N-dialkylaniline (e.g., N,N-dimethylaniline) in combinationwith a metal in an oxidized state, a peroxide, or a persulfate. Specificarylsulfinate salts include tetraalkylammonium arylsulfinates such astetrabutylammonium 4-ethoxycarbonylbenzenesulfinate, tetrabutylammonium4-trifluoromethylbenzenesulfinate, and tetrabutylammonium3-trifluoromethylbenzenesulfinate. Specific triarylsulfonium saltsinclude those with a triphenylsulfonium cation and with an anionselected from PF₆ ⁻, AsF₆ ⁻, and SbF₆ ⁻. Suitable metal ions include,for example, ions of group III metals, transition metals, and lanthanidemetals. Specific metal ions include, but are not limited to, Fe(III),Co(III), Ag(I), Ag(II), Cu(II), Ce(III), Al(III), Mo(VI), and Zn(II).Suitable peroxides include benzoyl peroxide, lauroyl peroxide, and thelike. Suitable persulfates include, for example, ammonium persulfate,tetraalkylammonium persulfate (e.g., tetrabutylammonium persulfate), andthe like.

The polymerizable composition is typically free or substantially free ofsurfactants. As used herein, the term “substantially free” in referenceto the surfactant means that no surfactant is purposefully added to thepolymerizable composition and any surfactant that may be present is theresult of being an impurity in one of the components of thepolymerizable composition (e.g., an impurity in the organic solvent orin one of the monomers). The polymerizable composition typicallycontains less than 0.5 weight percent, less than 0.3 weight percent,less than 0.2 weight percent, less than 0.1 weight percent, less than0.05 weight percent, or less than 0.01 weight percent surfactant basedon the total weight of the polymerizable composition. The absence of asurfactant is advantageous because these materials tend to restrictaccess to and, in some cases, fill micropores and mesopores in a porousmaterial.

When the polymerizable composition is heated in the presence of a freeradical initiator, polymerization of the monomers in the monomer mixtureoccurs. By balancing the amounts of each monomer in the monomer mixtureand by selection of an organic solvent that can solubilize all of themonomers and the growing polymeric material during its early formationstage, a non-hydrolyzed precursor polymer can be prepared that has a BETspecific surface area equal to at least 350 m²/gram. The BET specificsurface area of the non-hydrolyzed precursor polymer can be at least 400m²/gram, at least 450 m²/gram, or at least 500 m²/gram. The BET specificsurface area can be, for example, up to 1000 m²/gram or higher, up to900 m²/gram, up to 800 m²/gram, up to 750 m²/gram, or up to 700 m²/gram.

The non-hydrolyzed precursor polymer is a granular material that can betreated with a hydrolyzing agent to provide a hydrolyzed polymericmaterial, which is the porous polymeric sorbent. The hydrolyzing agentreacts with the maleic anhydride monomeric units resulting in theformation of the monomeric units of Formula (I) that have two carboxylicacid groups (—COOH groups). Any suitable hydrolyzing agent that canreact with the anhydride group (—(CO)—O—(CO)—) of the maleic anhydridemonomeric units can be used. In many embodiments, the hydrolyzing agentis a base such as a basic material dissolved in water. One example basicmaterial is an alkali metal hydroxide such as sodium hydroxide (e.g., anaqueous solution of sodium hydroxide). Alternatively, the hydrolyzingagent could be water alone at elevated temperatures (e.g., above roomtemperature to boiling) or a dilute acid at slightly elevatedtemperatures (e.g., above room temperature to about 80° C.). In manyembodiments, the preferred hydrolyzing agent is a base such as an alkalimetal hydroxide. The non-hydrolyzed precursor polymeric material ismixed with a solution of alkali metal hydroxide dissolved in an alcoholsuch as methanol. The mixture is heated at a temperature near 80° C. forseveral hours (e.g., 4 to 12 hours). The hydrolyzed polymeric materialcan then be treated with hydrochloric acid to convert any carboxylatesalts to carboxylic acid groups.

The hydrolyzed polymeric material, which is the polymeric sorbent, has aBET specific surface area less than that of the non-hydrolyzed precursorpolymeric material. The opening of the anhydride group may sufficientlyincrease the conformational freedom in the polymeric backbone resultingin decreased porosity. In addition, hydrogen bonding between carboxylicacids in the hydrolyzed polymeric material could possibly restrict orblock access to pores. The BET specific surface area of the hydrolyzedpolymeric material is often about 30 to 80 percent, 30 to 60 percent, 40to 80 percent, or 40 to 60 percent of the BET specific surface area ofthe non-hydrolyzed precursor polymeric material. Because of thisdecrease, it is often desirable to prepare a precursor polymericmaterial having the highest possible BET specific surface area yethaving sufficient solubility for carbon dioxide.

The polymeric sorbent typically has a BET specific surface area equal toat least 250 m²/gram. In some embodiments, the BET specific surface areais at least 275 m²/gram, at least 300 m²/gram, at least 325 m²/gram, orat least 350 m²/gram. The BET specific surface area can be up to 700m²/gram or higher, up to 600 m²/gram, up to 500 m²/gram, or up to 400m²/gram. In some embodiments, the BET specific surface area is in arange of 250 to 700 m²/gram, in a range of 250 to 500 m²/gram, or in arange of 300 to 500 m²/gram.

The high BET specific surface area is at least partially attributable tothe presence of micropores and/or mesopores in polymeric sorbent. Theargon adsorption isotherms (at 77° K) of the polymeric sorbent indicatethat there is considerable adsorption of argon at relative pressuresbelow 0.1, which suggests that micropores are present. There is agradual increase in adsorption at relative pressures between 0.1 andabout 0.95. This increase is indicative of a wide size distribution ofmesopores. An argon adsorption isotherm is shown in FIG. 2 for anexample porous polymeric sorbent.

In some embodiments, at least 20 percent of the BET specific surfacearea of the polymeric sorbent is attributable to the presence ofmicropores and/or mesopores. The percentage of the BET specific surfacearea attributable to the presence of micropores and/or mesopores can beat least 25 percent, at least 30 percent, at least 40 percent, at least50 percent, or at least 60 percent. In some embodiments, the percentageof the BET specific surface area attributable to the presence ofmicropores and/or mesopores can be up to 90 percent or higher, up to 80percent or higher, or up to 75 percent or higher.

The porous polymeric sorbent has a total pore volume equal to at least0.20 cm³/gram. Total pore volume is calculated from the amount of argonadsorbed at liquid nitrogen temperature (77° K) at a relativepressure)(p/p° equal to approximately 0.98 (i.e., 0.98±0.01). In someembodiments, the total pore volume is at least 0.25 cm³/gram, at least0.30 cm³/grams, at least 0.40 cm³/gram, at least 0.50 cm³/gram, or atleast 0.60 cm³/gram. The total pore volume can be up to 1.0 cm³/gram oreven higher, up to 0.9 cm³/gram, up to 0.8 cm³/gram, or up to 0.7cm³/gram.

The structure of the divinylbenzene/maleic anhydride polymeric materialis particularly well suited for use as a precursor polymeric materialfor the porous polymeric sorbent. Providing that the content ofmonomeric units of Formula (III) are low, the divinylbenzene/maleicanhydride precursor polymeric material has alternating monomeric unitsfrom divinylbenzene and maleic anhydride. This structure results in highcrosslinking and contributes to the formation of a porous polymericmaterial, particularly a porous polymeric material having a high contentof micropores and/or mesopores. The replacement of maleic anhydride withan ethylenically unsaturated monomer may not result in the formation ofa polymeric material that has such high BET specific surface area and alarge pore volume.

The porous polymeric sorbent sorbs carbon dioxide. Thus, in anotheraspect, a composition is provided that includes the porous polymericsorbent and carbon dioxide sorbed on the porous polymeric sorbent. Theporous polymeric sorbent is the same as described above. The amount ofcarbon dioxide that sorbs on the porous polymeric sorbent tends toincrease with pressure. For example, the amount of carbon dioxide sorbedin mmoles/gram at room temperature (e.g., 25° C.) and 20 bar is often atleast 2.5 times greater than the amount sorbed in mmoles/gram at roomtemperature (e.g., 25° C.) and 1 bar. That is, the ratio of the amountsorbed in mmoles/gram at room temperature (e.g., 25° C.) and 20 bar tothe amount sorbed in mmoles/gram at room temperature (e.g., 25° C.) and1 bar is at least 2.5. For example, this ratio can be at least 3, atleast 4, or at least 5 and can be up to 10 or more, up to 9, up to 8, orup to 7. Stated differently, the difference in the amount of carbondioxide sorbed at room temperature (e.g., 25° C.) and 20 bar and theamount of carbon dioxide sorbed at room temperature (e.g., 25° C.) and 1bar is often at least 1.5 mmoles/gram or at least 2 mmoles/gram. Thisamount can be up to 10 mmoles/gram, up to 8 mmoles/gram, up to 6mmoles/gram, or up to 4 mmoles/gram.

The amount of carbon dioxide sorbed at room temperature (e.g., 25° C.)and 20 bar is often at least 2 mmoles/gram, at least 2.5 mmoles/gram, atleast 3 mmoles/gram, at least 3.5 mmoles/gram, at least 4 mmoles/gram,at least 4.5 mmoles/gram, at least 5 mmoles/gram, at least 5.5mmoles/gram, at least 6 mmoles/gram, at least 7 mmoles/gram, at least 8mmoles/gram, or at least 10 mmoles/gram.

The amount of carbon dioxide sorbed at room temperature (e.g., 25° C.)and 20 bar is often at least 10 weight percent based on the weight ofthe polymeric sorbent. The amount sorbed can be at least 12 weightpercent, at least 14 weight percent, at least 16 weight percent, atleast 18 weight percent, at least 20 weight percent, at least 22 weightpercent, at least 24 weight percent, at least 25 weight percent, atleast 30 weight percent, at least 35 weight percent, at least 40 weightpercent, or at least 45 weight percent.

FIG. 1 is a plot showing the adsorption and desorption of both carbondioxide and methane at pressures up to about 20 bar at 25° C. for anexample porous polymeric sorbent. There is only a small amount ofhysteresis between the adsorption and desorption curves. This maysuggest that the pores of the polymeric sorbent can be both filled andemptied easily with either carbon dioxide or methane. The amount ofcarbon dioxide that is sorbed at a first pressure such as, for example,at 20 bar or even greater can be reduced substantially by simplydecreasing the pressure to a second pressure that is lower than thefirst pressure. The second pressure is often greater than or equal to 1bar or ambient pressure. No vacuum or heat is needed to substantiallyreduce the amount of carbon dioxide sorbed on the porous polymericsorbent at room temperature (e.g., 25° C.). For example, the amount ofcarbon dioxide sorbed at room temperature (e.g., 25° C.) and 20 bar canbe reduced by at least 60 weight percent, at least 70 weight percent, atleast 80 weight percent, or at least 90 weight percent by lowering thepressure to about 1 bar. The porous polymeric sorbent can be usedrepeatedly to sorb and to desorb carbon dioxide by cycling the pressurefrom a first pressure such as, for example, about 20 bar to a secondpressure such as, for example, about 1 bar.

The polymeric sorbent selectively sorbs carbon dioxide over methane. Forexample, the amount of sorbed carbon dioxide at room temperature (e.g.,25° C.) and 20 bar is often at least 2 times greater than the amount ofsorbed methane at room temperature (e.g., 25° C.) and 20 bar. That is,the ratio of the amount of carbon dioxide (in mmoles/gram) to the amountof methane (in mmoles/gram) sorbed at room temperature (e.g., 25° C.)and 20 bar is at least 2. For example, this ratio can be at least 2.5,at least 3, at least 3.5, at least 4, at least 4.5, or at least 5 andcan be up to 10, up to 8, or up to 6. Selectivity for the sorption ofcarbon dioxide over hydrogen is expected to be at least as good as theselectivity for the sorption of carbon dioxide over methane.

Other hyper-crosslinked polymeric materials that have been used forsorption of carbon dioxide have no functional groups. More specifically,these previously used polymeric materials are aromatic hydrocarbon-basedsorbents. While such polymeric materials are likely to have low watersorption, they may not be as effective as the porous polymeric sorbentsdescribed herein that have carboxylic acid groups. Although not wishingto be bound by theory, the carboxylic acid groups may facilitatesolubility of the carbon dioxide within the porous polymeric sorbents.That is, sorption may occur by a combination of pore filling andswelling of the porous polymeric sorbent.

Various embodiments are provided that are methods of sorbing carbondioxide on a porous polymeric sorbent and a composition resulting fromthe sorption of carbon dioxide on the porous polymeric sorbent. Theporous polymeric sorbent is a hydrolyzed divinylbenzene/maleic anhydridepolymeric material that has micropores and/or mesopores.

Embodiment 1A is a method of sorbing carbon dioxide on a porouspolymeric sorbent. The method includes providing a polymeric sorbenthaving a BET specific surface area equal to at least 250 m²/gram. Theporous polymeric sorbent contains (a) 8 to 40 weight percent of a firstmonomeric unit of Formula (I),

-   -   (b) 48 to 75 weight percent of a second monomeric unit of        Formula (II),

(c) 0 to 20 weight percent of a third monomeric unit of Formula (III)wherein R¹ is hydrogen or alkyl,

and (d) 0 to 8 weight percent of a fourth monomeric unit of Formula(IV).

Each weight percent value is based on a total weight of the porouspolymeric sorbent. Each asterisk (*) denotes the location of attachmentof the monomeric unit to another monomeric unit or to a terminal group.The method further includes exposing the porous polymeric sorbent to agas mixture containing carbon dioxide and sorbing carbon dioxide on theporous polymeric sorbent.

Embodiment 2A is the method of embodiment 1A, wherein at least 95 weightpercent, at least 99 weight percent or 100 weight percent of themonomeric units in the porous polymeric sorbent are of Formula (I),Formula (II), Formula (III), and Formula (IV).

Embodiment 3A is the method of embodiment 1A or 2A, wherein the porouspolymeric sorbent comprises (a) 10 to 40 weight percent monomeric unitsof Formula (I), (b) 50 to 75 weight percent monomeric units of Formula(II), (c) 1 to 20 weight percent monomeric units of Formula (III), and(d) 0 to 8 weight percent monomeric units of Formula (IV).

Embodiment 4A is the method of any one of embodiments 1A to 3A, whereinthe porous polymeric sorbent comprises (a) 15 to 35 weight percentmonomeric units of Formula (I), (b) 55 to 75 weight percent monomericunits of Formula (II), (c) 1 to 20 weight percent monomeric units ofFormula (III), and (d) 0 to 7 weight percent monomeric units of Formula(IV).

Embodiment 5A is the method of any one of embodiments 1A to 4A, whereinthe porous polymeric sorbent comprises (a) 20 to 30 weight percentmonomeric units of Formula (I), (b) 55 to 75 weight percent monomericunits of Formula (II), (c) 1 to 20 weight percent monomeric units ofFormula (III), and (d) 0 to 6 weight percent monomeric units of Formula(IV).

Embodiment 6A is the method of any one of embodiments 1A to 5A, whereinthe porous polymeric sorbent comprises (a) 20 to 35 weight percentmonomeric units of Formula (I), (b) 55 to 70 weight percent monomericunits of Formula (II), (c) 1 to 20 weight percent monomeric units ofFormula (III), and (d) 0 to 7 weight percent monomeric units of Formula(IV).

Embodiment 7A is the method of any one of embodiments 1A to 6A, whereinthe porous polymeric sorbent comprises (a) 20 to 40 weight percentmonomeric units of Formula (I), (b) 50 to 70 weight percent monomericunits of Formula (II), (c) 5 to 20 weight percent monomeric units ofFormula (III), and (d) 0 to 8 weight percent monomeric units of Formula(IV).

Embodiment 8A is the method of any one of embodiments 1A to 7A, whereinthe porous polymeric sorbent has a total pore volume of at least 0.20cm³/gram, the total pore volume being measured by adsorbing argon at 77°K at a relative pressure equal to 0.98±0.01.

Embodiment 9A is the method of any one of embodiments 1A to 8A, whereinthe total pore volume is at least 0.25 cm³/gram or at least 0.30cm³/gram.

Embodiment 10A is the method of any one of embodiments 1A to 9A, whereinthe BET specific surface area of the porous polymeric sorbent is atleast 300 m²/gram.

Embodiment 11A is the method of any one of embodiments 1A to 10A,wherein the BET specific surface area of the porous polymeric sorbent isat least 350 m²/gram.

Embodiment 12A is the method of any one of embodiments 1A to 11A,wherein at least 20 percent of the BET specific surface area isattributable to micropores, mesopores, or a combination thereof.

Embodiment 13A is the method of any one of embodiments 1A to 12A,wherein at least 50 percent of the BET specific surface area isattributable to micropores, mesopores, or a combination thereof.

Embodiment 14A is the method of any one of embodiments 1A to 13A,wherein an amount of carbon dioxide sorbed on the porous polymericsorbent is at least 2 mmoles/gram (i.e., 2 mmoles carbon dioxide pergram of porous polymeric sorbent) at room temperature (e.g., 25° C.) and20 bar.

Embodiment 15A is the method of any one of embodiments 1A to 14A,wherein an amount of carbon dioxide sorbed on the porous polymericsorbent is at least 2.5 mmoles/gram or at least 3 mmoles/gram at roomtemperature (e.g., 25° C.) and 20 bar.

Embodiment 16A is the method of any one of embodiments 1A to 15A,wherein an amount of carbon dioxide sorbed on the porous polymericsorbent in mmoles/gram is at least 2.5 times greater at room temperature(e.g., 25° C.) and 20 bar than at room temperature (e.g., 25° C.) and 1bar.

Embodiment 17A is the method of any one of embodiments 1A to 16A,wherein an amount of carbon dioxide sorbed on the porous polymericsorbent in mmoles/gram is at least 3 times greater or at least 4 timesgreater at room temperature (e.g., 25° C.) and 20 bar than at roomtemperature (e.g., 25° C.) and 1 bar.

Embodiment 18A is the method of any one of embodiments 1A to 17A,wherein sorbing occurs at a first pressure and the method furthercomprises removing carbon dioxide sorbed on the porous polymeric sorbentat a second pressure that is lower than the first pressure and that isgreater than or equal to ambient pressure or 1 bar.

Embodiment 19A is the method of any one of embodiments 1A to 18A,wherein the gas mixture comprises carbon dioxide and methane and whereinan amount of carbon dioxide sorbed on the porous polymeric sorbent inmmoles/gram at room temperature (e.g., 25° C.) and 20 bar is at least 2times greater than an amount of methane sorbed on the porous polymericsorbent in mmoles/gram at room temperature (e.g., 25° C.) and 20 bar.

Embodiment 1B is a composition that includes (a) a porous polymericsorbent having a BET specific surface area equal to at least 250 m²/gramand (b) carbon dioxide sorbed on the porous polymeric sorbent. Theporous polymeric sorbent contains (a) 8 to 40 weight percent of a firstmonomeric unit of Formula (I),

(b) 48 to 75 weight percent of a second monomeric unit of Formula (II),

(c) 0 to 20 weight percent of a third monomeric unit of Formula (III)wherein R¹ is hydrogen or alkyl,

and (d) 0 to 8 weight percent of a fourth monomeric unit of Formula(IV).

Embodiment 2B is the composition of embodiment 1B, wherein at least 95weight percent, at least 99 weight percent or 100 weight percent of themonomeric units in the porous polymeric sorbent are of Formula (I),Formula (II), Formula (III), and Formula (IV).

Embodiment 3B is the composition of embodiment 1B or 2B, wherein theporous polymeric sorbent comprises (a) 10 to 40 weight percent monomericunits of Formula (I), (b) 50 to 75 weight percent monomeric units ofFormula (II), (c) 1 to 20 weight percent monomeric units of Formula(III), and (d) 0 to 8 weight percent monomeric units of Formula (IV).

Embodiment 4B is the composition of any one of embodiments 1B to 3B,wherein the porous polymeric sorbent comprises (a) 15 to 35 weightpercent monomeric units of Formula (I), (b) 55 to 75 weight percentmonomeric units of Formula (II), (c) 1 to 20 weight percent monomericunits of Formula (III), and (d) 0 to 7 weight percent monomeric units ofFormula (IV).

Embodiment 5B is the composition of any one of embodiments 1B to 4B,wherein the porous polymeric sorbent comprises (a) 20 to 30 weightpercent monomeric units of Formula (I), (b) 55 to 75 weight percentmonomeric units of Formula (II), (c) 1 to 20 weight percent monomericunits of Formula (III), and (d) 0 to 6 weight percent monomeric units ofFormula (IV).

Embodiment 6B is the composition of any one of embodiments 1B to 5B,wherein the porous polymeric sorbent comprises (a) 20 to 35 weightpercent monomeric units of Formula (I), (b) 55 to 70 weight percentmonomeric units of Formula (II), (c) 1 to 20 weight percent monomericunits of Formula (III), and (d) 0 to 7 weight percent monomeric units ofFormula (IV).

Embodiment 7B is the composition of any one of embodiments 1B to 6B,wherein the polymeric sorbent comprises (a) 20 to 40 weight percentmonomeric units of Formula (I), (b) 50 to 70 weight percent monomericunits of Formula (II), (c) 5 to 20 weight percent monomeric units ofFormula (III), and (d) 0 to 8 weight percent monomeric units of Formula(IV).

Embodiment 8B is the composition of any one of embodiments 1B to 7B,wherein the porous polymeric sorbent has a total pore volume of at least0.20 cm³/gram, the total pore volume being measured by adsorbing argonat 77° K at a relative pressure equal to 0.98±0.01.

Embodiment 9B is the composition of any one of embodiments 1B to 8B,wherein the total pore volume is at least 0.25 cm³/gram or at least 0.30cm³/gram.

Embodiment 10B is the composition of any one of embodiments 1B to 9B,wherein the BET specific surface area of the porous polymeric sorbent isat least 300 m²/gram.

Embodiment 11B is the composition of any one of embodiments 1B to 10B,wherein the BET specific surface area of the porous polymeric sorbent isat least 350 m²/gram.

Embodiment 12B is the composition of any one of embodiments 1B to 11B,wherein at least 20 percent of the BET specific surface area isattributable to micropores, mesopores, or a combination thereof.

Embodiment 13B is the composition of any one of embodiments 1B to 12B,wherein at least 50 percent of the BET specific surface area isattributable to micropores, mesopores, or a combination thereof.

Embodiment 14B is the composition of any one of embodiments 1B to 13B,wherein an amount of carbon dioxide sorbed on the porous polymericsorbent is at least 2 mmoles/gram (i.e., 2 mmoles carbon dioxide pergram of porous polymeric sorbent) at room temperature (e.g., 25° C.) and20 bar.

Embodiment 15B is the composition of any one of embodiments 1B to 14B,wherein an amount of carbon dioxide sorbed on the porous polymericsorbent is at least 2.5 mmoles/gram or at least 3 mmoles/gram at roomtemperature (e.g., 25° C.) and 20 bar.

Embodiment 16B is the composition of any one of embodiments 1B to 15B,wherein an amount of carbon dioxide sorbed on the porous polymericsorbent in mmoles/gram is at least 2.5 times greater at room temperature(e.g., 25° C.) and 20 bar than at room temperature (e.g., 25° C.) and 1bar.

Embodiment 17B is the composition of any one of embodiments 1B to 16B,wherein an amount of carbon dioxide sorbed on the porous polymericsorbent in mmoles/gram is at least 3 times greater or at least 4 timesgreater at room temperature (e.g., 25° C.) and 20 bar than at roomtemperature (e.g., 25° C.) and 1 bar.

EXAMPLES

TABLE 1 List of materials Chemical Name Chemical Supplier Divinylbenzene(DVB) (80% Sigma-Aldrich, Milwaukee, WI tech grade), which contained 80weight percent DVB and 20 weight percent styrene-type monomers. Thecalculation of moles of DVB used to prepare the polymeric material doestake into account the purity. Maleic anhydride (MA) Alfa Aesar, WardHill, MA Benzoyl peroxide (BPO) Sigma-Aldrich, Milwaukee, WI Ethylacetate (EtOAc) EMD Millipore Chemicals, Billerica, MA Sodium hydroxide(NaOH) EMD Millipore Chemicals, Billerica, MA Methanol (MeOH) BDH MerckLtd., Poole Dorset, UK Hydrochloric acid (HCl) (0.1N J.T. Baker -Avantor Performance volumetric solution) Materials, Center Valley, PAArgon Adsorption Analysis:

Porosity and gas sorption experiments were performed using aMicromeritics Instrument Corporation (Norcross, Ga.) accelerated surfacearea and porosimetry (ASAP) 2020 system using adsorbates of ultra-highpurity. The following is a typical method used for the characterizationof the porosity within the exemplified porous polymeric sorbents. In aMicromeritics half inch diameter sample tube, 50-250 milligrams ofmaterial was degassed by heating under ultra-high vacuum (3-7micrometers Hg) on the analysis port of the ASAP 2020 to remove residualsolvent and other adsorbates. The degas procedure for the precursorpolymeric material was 2 hours at 150° C. The degas procedure for theporous polymeric sorbents was 2 hours at 80° C. Argon sorption isothermsat 77° K were obtained using low pressure dosing (5 cm³/g) at a relativepressure)(p/p° less than 0.1 and a pressure table of linearly spacedrelative pressure points in a range from 0.1 to 0.98. The method for allisotherms made use of the following equilibrium intervals: 90 seconds atp/p° less than 10⁻⁵, 40 seconds at p/p° in a range of 10⁻⁵ to 0.1, and20 seconds at p/p° greater than 0.1. Helium was used for the free spacedetermination, after argon sorption analysis, both at ambienttemperature and at 77° K. BET specific surface areas (SA_(BET)) werecalculated from argon adsorption data by multipointBrunauer-Emmett-Teller (BET) analysis. Apparent micropore distributionswere calculated from argon adsorption data by density functional theory(DFT) analysis using the argon at 77° K on carbon slit pores bynon-linear density functional theory (NLDFT) model. Total pore volumewas calculated from the total amount of argon adsorbed at a relativepressure)(p/p° equal to approximately 0.98. BET, DFT and total porevolume analyses were performed using Micromeritics MicroActive Version1.01 software.

Carbon Dioxide and Methane Adsorption Analysis:

A high pressure microgravimetric gas sorption system model IGA-001 fromHiden Analytical (Warrington, U.K.) was used to measure the CO₂ and CH₄adsorption isotherms for the porous polymeric sorbent at 25° C. Thisautomated instrument integrates precise computer-control and measurementof weight change, pressure, and temperature during measurements todetermine the gas adsorption/desorption isotherms of small quantities ofmaterials. The following is a general procedure for the CO₂ and CH₄adsorption/desorption isotherm measurement of the porous polymericsorbents exemplified.

Prior to measurements, approximately 100 mg of a porous polymericsorbent was loaded onto the quartz crucible provided with theinstrument. The crucible was then attached to the internal suspensionrods of the microbalance. The sample was degassed at 150° C. for 8 hoursunder high vacuum (<1 mmHg). After degassing, the weight of the samplewas recorded and set as the initial reference weight for adsorption.Ultrahigh purity gases (CO₂ or CH₄) were introduced in predeterminedpressure steps, starting from vacuum and going up to 20 bar. Duringmeasurements, the sample temperature was kept constant (25.0±0.05° C.)by using a circulating water bath. After each variation of pressure, theweight relaxation was monitored in real time by the instrument'ssoftware, and the asymptotic equilibrium weight was calculated. Afterequilibration at each pressure level, a new pressure change was caused,and the system moved to the next isotherm point. A normal cycleconsisted of an adsorption branch (vacuum to 20 bar) and a reverseddesorption branch (20 bar down to vacuum). Buoyancy corrections weremade by using the skeletal density of the porous polymeric sorbentobtained from helium pycnometry measurements. The precision ofgravimetric measurements is estimated to be ±0.01 wt. % for a 100 mgsample at a pressure of 20 bar.

Example 1

In a 5 L round-bottom flask, 80.3 grams (493 mmoles) of DVB (80 wt. %,tech grade), 30.3 grams (309 mmoles) of MA, and 2.25 grams (9.29 mmoles)of BPO were dissolved in 2153 grams of EtOAc. The polymerizablecomposition had 5.0 wt. % solids in EtOAc and contained a monomermixture (58.1 wt. % DVB, 27.3 wt. % MA, and 14.5 wt. % styrene-typemonomers based on the total weight of monomers) plus 2 wt. % BPO (basedon the total weight of monomers). The polymerizable composition wasbubbled with nitrogen for 30 minutes. The flask was then capped andplaced in a sand bath at 95° C. The polymerizable composition was heatedat this elevated temperature for 18 hours. A white precipitate that hadformed was isolated by vacuum filtration and washed with EtOAc. Thesolid was divided up and placed in three 32 ounce jars. The jars werethen each filled with 750 mL of EtOAc. The solids were allowed to standin EtOAc for one hour at room temperature. The solids were againisolated by vacuum filtration and washed with EtOAc. The solid wasdivided up again and placed in three 32 ounce jars. The jars were theneach filled with 750 mL of EtOAc. The solids were allowed to stand inEtOAc overnight. The solids were again isolated by vacuum filtration andwashed with EtOAc. The solid was then dried under high vacuum at 95° C.for eight hours. This precursor polymeric material had a SA_(BET) of637.6 m²/gram and a total pore volume of 0.637 cm³/gram (p/p° equal to0.971) as determined by argon adsorption.

In a 4 ounce jar, 3.5 grams (87.5 mmoles) of sodium hydroxide (NaOH) wasdissolved in 60 mL of methanol (MeOH). To this solution was added 0.50grams of the precursor polymeric material. The jar was then capped andplaced in a sand bath at 80° C. This suspension was heated at thiselevated temperature for 18 hours. The solid was isolated by vacuumfiltration and washed with deionized water. The solid was placed in a 20mL vial, and 10 mL of 0.1 M aqueous hydrogen chloride (HCl) was added.The solid was allowed to stand in the aqueous HCl for 30 minutes. Thesolid was again isolated by vacuum filtration and washed with deionizedwater. The solid was then dried under high vacuum at 80° C. for 18hours.

This porous polymeric sorbent had a SA_(BET) of 359.6 m²/grams and atotal pore volume of 0.359 cm³/grams (p/p° equal to 0.978) as determinedby argon sorption. The argon adsorption isotherm is shown in FIG. 2.This porous polymeric sorbent adsorbed 3.30 mmoles/gram (14.5 wt. %uptake) CO₂ at 20 bar and 0.61 mmoles/gram (2.7 wt. % uptake) CO₂ at 1bar. This porous polymeric sorbent adsorbed 1.18 mmoles/gram (1.9 wt. %uptake) CH₄ at 20 bar and 0.12 mmoles/gram (0.2 wt. % uptake) CH₄ at 1bar. FIG. 1 contains a plot for both carbon dioxide adsorption anddesorption, as well as, methane adsorption and desorption at variouspressures up to 20 bar for this porous polymeric sorbent.

We claim:
 1. A method of sorbing carbon dioxide on a porous polymericsorbent, the method comprising: providing the porous polymeric sorbent,wherein the porous polymeric sorbent has a BET specific surface areaequal to at least 250 m²/gram, the porous polymeric sorbent comprising(a) 8 to 40 weight percent of a first monomeric unit of Formula (I);

(b) 48 to 75 weight percent of a second monomeric unit of Formula (II);

(c) 0 to 20 weight percent of a third monomeric unit of Formula (III)wherein R1 is hydrogen or alkyl; and

(d) 0 to 8 weight percent of a fourth monomeric unit of Formula (IV);

exposing the porous polymeric sorbent to a gas mixture comprising carbondioxide; and sorbing carbon dioxide on the porous polymeric sorbent. 2.The method of claim 1, wherein the porous polymeric sorbent comprises(a) 20 to 40 weight percent of the first monomeric units of Formula (I),(b) 50 to 70 weight percent of the second monomeric units of Formula(II), (c) 5 to 20 weight percent of the third monomeric units of Formula(III), and (d) 0 to 8 weight percent of the fourth monomeric units ofFormula (IV).
 3. The method of claim 1, wherein the porous polymericsorbent has a total pore volume of at least 0.20 cm³/gram, the totalpore volume being measured by adsorbing argon at 77° K at a relativepressure equal to 0.98±0.01.
 4. The method of claim 1, wherein the BETspecific surface area of the porous polymeric sorbent is at least 300m²/gram.
 5. The method of claim 1, wherein at least 50 percent of theBET specific surface area is attributable to micropores, mesopores, or acombination thereof.
 6. The method of claim 1, wherein an amount ofcarbon dioxide sorbed on the porous polymeric sorbent is at least 2mmoles/gram at 25° C. and 20 bar.
 7. The method of claim 1, wherein anamount of carbon dioxide sorbed on the porous polymeric sorbent inmmoles/gram is at least 2.5 times greater at 25° C. and 20 bar than at25° C. and 1 bar.
 8. The method of claim 1, wherein sorbing occurs at afirst pressure and the method further comprises removing carbon dioxidesorbed on the porous polymeric sorbent at a second pressure that islower than the first pressure and that is greater than or equal to 1bar.
 9. The method of claim 1, wherein the gas mixture comprises carbondioxide and methane and wherein an amount of carbon dioxide sorbed onthe porous polymeric sorbent in mmoles/gram at 25° C. and 20 bar is atleast 2 times greater than an amount of methane sorbed on the porouspolymeric sorbent in mmoles/gram at 25° C. and 20 bar.
 10. A compositioncomprising: (a) a porous polymeric sorbent having a BET specific surfacearea equal to at least 250 m²/gram, the polymeric sorbent comprising (i)8 to 40 weight percent of a first monomeric unit of Formula (I);

(ii) 48 to 75 weight percent of a second monomeric unit of Formula (II);

(iii) 0 to 20 weight percent of a third monomeric unit of Formula (III)wherein R¹ is hydrogen or alkyl; and

(iv) 0 to 8 weight percent of a fourth monomeric unit of Formula (IV);and

(b) carbon dioxide sorbed on the porous polymeric sorbent.
 11. Thecomposition of claim 10, wherein the amount of carbon dioxide sorbed onthe porous polymeric sorbent at 20 bar and 25° C. is at least 2mmoles/gram.
 12. The composition of claim 10, wherein the porouspolymeric sorbent comprises (i) 20 to 40 weight percent of the firstmonomeric unit of Formula (I), (ii) 50 to 70 weight percent of thesecond monomeric unit of Formula (II), (iii) 5 to 20 weight percent ofthe third monomeric unit of Formula (III), and (iv) 0 to 8 weightpercent of the fourth monomeric units of Formula (IV).
 13. Thecomposition of claim 10, wherein the porous polymeric sorbent has atotal pore volume of at least 0.20 cm³/gram, the total pore volume beingmeasured by adsorbing argon at 77° K at a relative pressure equal to0.98±0.01.
 14. The composition of claim 10, wherein the BET specificsurface area of the porous polymeric sorbent is at least 300 m²/gram.15. The composition of claim 10, wherein an amount of carbon dioxidesorbed on the porous polymeric sorbent in mmoles/gram is at least 2.5times greater at 25° C. and 20 bar than at 25° C. and 1 bar.